1. Field of the Invention
The present invention relates, in general, to an impedance transformation-type wide band internal antenna and, more particularly, to an impedance transformation-type wide band antenna, in which a feeding part is formed in a multi-path structure to transform impedance, and is bent multiple times to generate a plurality of resonant frequencies, thus enabling the impedance transformation-type wide band antenna to be used both in a multiple band and in a wide band.
2. Description of the Related Art
Currently, services for wireless communication have changed from narrow band communication services to wide band communication services, such as the Internet or multimedia. Further, due to the need to develop an integrated system capable of providing multiple services through a single terminal, the antennas of wireless communication systems are required to have wide band characteristics together with integrated functions.
FIG. 1A is a perspective view showing a conventional single layer wide band antenna using stubs, and FIG. 1B is a bottom view of the wide band antenna of FIG. 1A.
As shown in FIG. 1A, a conventional antenna 10 includes a dielectric (substrate) 20 provided on the upper portion thereof, a patch 40 formed on the dielectric 20 to have a width less than that of the dielectric 20 and to have a hole 30 formed therein, thin plate-shaped conductive stubs 50 attached to the diagonal corners of the patch 40 and operated to transform the resonant frequency and impedance of the antenna 10 by converting the location and size of the conductive stubs 50, and a conductive ground plane 60 attached to the bottom surface of the dielectric 20.
As shown in FIG. 1B, the antenna 10 includes a coaxial cable 80 that is soldered with a feeding point 70 through a hole 30 formed in the patch 40 and is operated to provide an external signal source to the patch 40.
The patch 40 having a predetermined size is constructed in such a way that a first stub 51, attached to the upper left portion of the patch 40, and a second stub 52, attached to the lower right portion of the patch 40, are integrated with the patch 40. In this case, wide band characteristics can be realized only when the locations of the stubs 51 and 52 are designed so as to be exactly symmetrical around the center of the patch 40. If the stubs 51 and 52 are installed to be opposite each other, wide band characteristics cannot be realized in the antenna 10, and thus the stubs 51 and 52 are placed to be approximately symmetrical with each other around the center of the patch 40.
Meanwhile, the dielectric 20, disposed between the ground plane 60 and the patch 40, which is a radiation element, can be filled with an air layer according to the purpose of the antenna 10. A connector required to feed the antenna 10 is also placed to be spaced apart from the center of the antenna 10 by a predetermined distance in the direction of one side thereof, so that the impedance of the antenna can be adjusted using the location of the feeding point 70, together with the sizes of the stubs 51 and 52, thus obtaining wide band characteristics through impedance matching.
The conventional single layer wide band antenna using stubs is problematic in that, since the sizes of stubs or the location of a feeding point are changed so as to adjust the impedance thereof, there is a limitation in the space in which the antenna can actually be mounted in a wireless communication terminal, and since a multiple band must also be supported in the same antenna space, it is difficult to utilize such an antenna for a wireless communication system.